Mineral description : Prehnite

Prehnite from Bredsjönäs.
Notice the spherical form.

Mineral class Silicates : Phyllosilicate : Epidote - Vesuvian group.

Chemical formula Ca₂Al₂Si₃O₁₀(OH)₂

Crystal system Orthorombic.

Habitus Crystals prismatic, tabular or pyramidal, but usually as radiating botryoidal form or massive.

Cleavage Distinct with an uneven fracture.

Hardness 6-6.5

Density 2.90-2.95

Color Usually light green, can also be white yellow, gray or colorless.

Streak White.

Luster Vitreous to pearly, transparent to translucent.

Description

Occurance Usually in cavities in lavas.

Associates

Notes Gives off water when heated.

Locations Not so common mineral in Sweden.

Ädelfors and Kleva mines, Småland. As apple green crusts in cracks and cavities.
Jakobsbergsgruvan, Nordmark, Värmland. As thin white coatings in cracks.
Sjösa and Bredsjönäs, Södermanland. As crystals up to 0.5 cm.

To silicate index.
Mineral group index.
Main index.

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axelsson@acc.umu.se

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Last changed : 1998-03-07

Mineral class	Silicates : Phyllosilicate : Epidote - Vesuvian group.
Chemical formula	Ca₂Al₂Si₃O₁₀(OH)₂
Crystal system	Orthorombic.
Habitus	Crystals prismatic, tabular or pyramidal, but usually as radiating botryoidal form or massive.
Cleavage	Distinct with an uneven fracture.
Hardness	6-6.5
Density	2.90-2.95
Color	Usually light green, can also be white yellow, gray or colorless.
Streak	White.
Luster	Vitreous to pearly, transparent to translucent.
Description
Occurance	Usually in cavities in lavas.
Associates
Notes	Gives off water when heated.
Locations	Not so common mineral in Sweden. Ädelfors and Kleva mines, Småland. As apple green crusts in cracks and cavities. Jakobsbergsgruvan, Nordmark, Värmland. As thin white coatings in cracks. Sjösa and Bredsjönäs, Södermanland. As crystals up to 0.5 cm.